High microbiological quality water with high clarity is a scarce resource that is currently required for the processes of many industries. The treatment for obtaining such water entails large investment and operating costs, and the processes are complicated and present many problems that have not been effectively solved to the present day. Also, the processes consume large amounts of energy and chemicals, thus severely damaging the environment. Specifically, removing impurities that are contained in the water, such as suspended solids, metals, algae, and bacteria, among others, requires the installation of expensive and complex filtration systems that allow filtering the entire volume of water, thus presenting high energy consumption, high chemical and material requirements, and other resources that hinder this process.
High microbiological quality water is required for several important processes, such as the pretreatment of water for reverse osmosis desalination processes, for treating water used in aquaculture, for treating and maintaining water for the potable water industry, for treating industrial liquid residuals, or for mining industries, among others. The water of high microbiological quality and clarity at very low costs of the present invention can also be used in other industrial processes that require high physicochemical and microbiological quality water.
Desalination
There are several reasons for addressing the improvement of current desalination processes, since this industry is growing exponentially and will be very important in the future. From the total water available in the world, 97% of it corresponds to seawater. From the remaining 3% of fresh water available, 2.1% is frozen in the poles and only a 0.9% is available for human consumption, which is found in rivers, lakes, or as groundwater. The limited availability of freshwater for human consumption is a problem that has been increasing along with global population growth and cultural change. About 40% of the world's population already suffers from problems caused by lack of access to sources of freshwater.
Thus, just as the United Nations Environment Programme (UNEP) has warned, it is expected that nearly 3 billion people will suffer from severe water shortages within the next 50 years. Also, in 1999, the UNEP identified the shortage of water along with global warming as the biggest problems for the new millennium. The freshwater resources are being consumed at a rate greater than nature can replenish them, and also, pollution and exploitation of groundwater and surface water have led to a decrease in the quantity and/or quality of available natural resources. The combination of increasing population, the lack of new sources of freshwater, and the increasing of per capita water consumption, causes an aggravation of regional tensions among countries that are located near water resources. All of the above obligates to find a solution to the problem of water availability, not only to meet the future demands of humanity, but also to avoid the conflicts that water shortages can lead to.
Conveniently, seawater is the most abundant resource on earth, a virtually inexhaustible source of salt water which is always available for use. Therefore, to solve the immense problems associated with the short supply of fresh water, the best solution is to process sea water to provide fresh water for general consumption. The vast availability of sea water contained in the oceans has led to research and creation of technologies to remove the salts in the water by various processes, and produce fresh water. The best available technology in the world to achieve this objective is the desalination process. Currently, about 130 countries worldwide are implementing some type of desalination process, and it is expected that the installed capacity will be doubled by 2015.
The two most used desalination processes are:                Using water evaporation, as a distillation process, in such a way to evaporate only the water molecules, leaving behind all salts and dissolved minerals. This process is called thermal desalination.        Using special membranes which allow performing the reverse osmosis process, separating the water from salts through application of pressure on a semi-permeable membrane. This process is called reverse osmosis.        
To decide between what process to use, energy consumption is an important factor to consider. It is estimated that the consumption of energy to produce 1 m3 of water using thermal desalination is between 10 to 15 kWh/m3, while a process using reverse osmosis technology uses about 5 kWh/m3. This is because thermal desalination requires evaporation, so more energy is needed for the phase change process, making thermal desalination less efficient in terms of energy consumption. Current restrictions require improving the overall efficiency of processes, using technologies that meet the environmental requirements demanded by society, while minimizing the carbon footprint and the environmental impact.
In terms of the evolution of the mentioned technologies, since 2005 the global installed capacity of reverse osmosis desalination plants has exceeded the installed capacity of thermal plants. The projection is that by 2015 the world's desalination capacity will be distributed by 62% in reverse osmosis plants and 38% in thermal desalination plants. In fact, the global capacity to produce fresh water in desalination plants using reverse osmosis technologies has increased by over 300% in just 6 years.
Reverse osmosis is a process by which pressure is applied to a flow of water having a high concentration of salts, through a semi-permeable membrane that only lets water molecules to pass through. Because of this, the permeate leaving the other side of the membrane corresponds to high microbiological quality water with a low salt content. Within the operation of desalination plants using reverse osmosis technology, there are 2 main stages:                1. Water pretreatment        2. Desalination Stage        
The second stage, corresponding to the reverse osmosis process itself, has been extensively studied and efficiencies of up to 98% have been achieved (General Electric HERO Systems).
The first stage of the process of producing fresh water using reverse osmosis corresponds to the conditioning of salt water before reaching the semi-permeable membrane, also called water pretreatment. This pretreatment step experiences major problems related to water quality needed for efficient operation of reverse osmosis membranes. In fact, it is estimated that 51% of reverse osmosis membranes fail due to poor pretreatment, either due to poor design or poor operation, while 30% fail because of inadequate dosing of chemicals. Current methods, in addition to being inefficient due to high rate of failures, have very high costs thereby driving research to find new methods that solve these problems.
The problems arising in the membranes depend on the characteristics of feed water, which fouls the filters and membranes located prior to pretreatment and also the reverse osmosis membranes. These problems are reflected in a shorter life and higher frequencies of maintenance and cleaning of the membranes, leading to higher costs of operation and maintenance. Common problems that arise due to poor water pretreatment are divided into 2 types: damage of the membranes and blocking of the membranes.
The damage of reverse osmosis membranes is mainly caused by oxidation and hydrolysis of membrane material because of diverse compounds in the feed water. Most reverse osmosis membranes cannot withstand existing concentrations of residual chlorine, which is usually added in desalination processes to prevent biological growth. The membranes have high costs, so all possible precautions to maintain continuous operation and achieve the best possible performance should be taken; thus, the water must be often de-chlorinated before it passes through the membranes. Eventually, the pH of the feed water should also be adjusted for optimal operation of the membranes. In addition, dissolved oxygen and other oxidizing agents must be removed to prevent damage to the membranes. The gases also affect the proper operation of the membranes, so high concentrations should be avoided for optimal operation. Current methods to regulate the concentrations of gases and oxidizing agents are very expensive and inefficient.
On the other hand, blocking of reverse osmosis membranes is largely responsible for the large inefficiencies that arise because of various reasons, for example, higher pressures need to be applied on the feed water to pass through the membrane, major downtime is caused by the constant maintenance and washing that has to be performed, and the high replacement costs of supplies used in the process. The blocking of the membranes is caused by three major problems: biofouling, scaling and colloidal fouling.
Biofouling is caused by the growth of colonies of bacteria or algae on the surface of the membrane. Because chlorine cannot be used, the risk of developing a film of biomass exists, thus preventing the passage of water supply and reducing the efficiency of the system.
Another major problem that causes blockage of the membrane is scaling which finally causes their obstruction. Scaling refers to precipitation and deposits of moderately soluble salt on the membranes. In fact, under certain operating conditions, the solubility limits of some of the components present in the feed water may be exceeded, allowing precipitation. These components include calcium carbonate, magnesium carbonate, calcium sulfate, silica, barium sulfate, strontium sulfate and calcium fluoride, among others. In reverse osmosis units, the final stage is subject to the highest concentration of dissolved salts, and this is where the first signs of scaling begin to appear. Scaling due to precipitation is amplified by the phenomenon of concentration gradient on the surface of the membranes.
Obstruction by particles or colloidal fouling occurs when the water supply contains a large amount of suspended particles and colloidal matter, requiring constant washing to clean the membranes. The concentration of particles in water can be measured and expressed in different ways. The most used parameter is the turbidity, which must be maintained at low levels for proper operation. The accumulation of particles on the surface of the membrane can adversely affect both the feed water flow and the rejection properties of reverse osmosis membrane. The colloidal fouling is caused by the accumulation of colloidal particles on the surface of the membrane and the formation of a layer with a cake form. The decrease in permeate flux is given on the one hand by the formation of a cake layer, and on the other hand, because of the high concentration of salt in the membrane surface caused by the obstructed diffusion of salt ions, causing an increased osmotic pressure which reduces the net force impulse. The monitored parameter to prevent colloidal fouling is the Silt Density Index (SDI), and membrane manufacturers suggest SD's of up to 4. Blockage of the membranes can also occur due to fouling by Natural Organic Matter (NOM). The natural organic matter clogs the membrane either because: the narrowing of pores associated with the adsorption of natural organic matter on the walls of the pores, colloidal organic matter which acts as a stopper at the opening of the pores, or forming a continuous layer of gel that coats the surface of the membrane. This layer creates great inefficiencies and clogging of this layer should therefore be avoided at all costs.
Currently, the pretreatment of water before entering the desalination process generally includes the following steps:                1. Chlorination to reduce organic and bacteriological load in raw water        2. Sand filtration to reduce turbidity        3. Acidification to reduce pH and reduce calcareous processes        4. Inhibition of calcium and barium scales using antiscalants        5. Dechlorination to remove residual chlorine        6. Particle filtering cartridges required by membrane manufacturers        7. Microfiltration (MF), Ultrafiltration (UF) and Nanofiltration (NF)        
Among the pretreatment steps above, the costs of filtration steps, either with sand filters or more sophisticated filtration steps such as microfiltration, ultrafiltration or nanofiltration, leads to high costs along with a number of drawbacks. In particular, if the pretreatment is inadequate, the filters become clogged with organic matter, colloids, algae, microorganisms, and/or larvae. In addition, the requirement to filter the total volume of water to be processed in the plant to reduce turbidity and remove particles imposes severe restrictions in terms of energy, implementation and installation costs, as well as during the operation in terms of maintenance and replacement of filters. In addition, pretreatment systems today are very inefficient and have high costs due to the devices to be implemented, and the continuing operating and maintenance tasks that are costly and difficult to perform.
In summary, increasingly scarce freshwater resources has created a worldwide supply problem that has resulted in the design and implementation of various desalination technologies. Reverse osmosis desalination is a promising technology for addressing the increasing scarcity of freshwater resources, and this technology is projected to have significant growth in the future. However, a cost effective and energy efficient means of pretreating the feed water poses a significant problem for reverse osmosis desalination plants. An efficient technology that operates at low costs and is able to produce water of sufficient quality for its use as raw material in desalination processes is needed.
Aquaculture Industry
The aquaculture industry is focused on farming of aquatic species, plants and animals, from which raw materials for food, chemical, and pharmaceutical industries, among others, is obtained. The aquatic species are grown in fresh or sea water, where mainly fish, mollusks, crustaceans, macro-algae and microalgae are cultivated. Due to industry growth, development of new technologies, and environmental regulations imposed by the international community, there is a need to minimize the environmental impact of the aquaculture industry while at the same time maintaining adequate control of the operation conditions. To do this, the cultivation of aquatic species have migrated from being located in situ in natural water sources, such as the sea, to facilities built specifically for such purposes.
Besides the traditional culture of these species as raw material in food, pharmaceutical industries and general manufacturing, aquatic species are also used in the energy sector to generate energy from renewable non-conventional sources, in particular, for the production of biofuels such as biodiesel from microalgae.
With regard to biofuels, it should be noted that the global energy matrix is organized around fossil fuels (oil, gas and coal), which provide about 80% of global energy consumption. Biomass, hydroelectric, and other “non-conventional” energy sources, such as solar energy, are renewable energy sources. Within the latter group, and representing only 2.1% of the matrix, are comprised eolic energy, solar energy, and biofuels, which in turn include biogas, biodiesel and ethanol, mainly.
Because the sources of fossil and nuclear energy are finite, future demand may not be supplied. Accordingly, energy policy in developing countries is considering the introduction of alternative energies. Additionally, the abuse of conventional energy like oil and coal, among others, lead to problems such as pollution, increased greenhouse gases and the depletion of the ozone layer. Therefore, the production of clean, renewable, and alternative energies is an economic and environmental need. In some countries, the use biofuels blended with petroleum fuels, has forced massive and efficient production of biodiesel, which can be obtained from vegetable oil, animal fats and algae.
The production of biodiesel from algae does not require the extensive use of agricultural land. Thus, it does not affect food production worldwide, because the algae can grow in reduced spaces and have very fast growth rates, with biomass doubling times of 24 hours. Consequently, algae are a source of continuous and inexhaustible energy production, and also absorb carbon dioxide for their growth, which can be captured from various sources such as thermal power stations.
The main systems for microalgae growth correspond to:                Lakes: Since algae require sun light, carbon dioxide, and water, they can be grown in lakes and open ponds.        Photo bioreactors: A photo bioreactor is a controlled and closed system including a source of light, which by being closed require the addition of carbon dioxide, water and light.        
With respect to lakes, algae cultivation in open ponds has been extensively studied. This category of ponds are natural water bodies (lakes, lagoons, ponds, sea) and artificial ponds or containers. The most commonly used systems are large ponds, tanks, circular ponds and shallow raceway ponds. One of the main advantages of open ponds is that they are easier to construct and operate than most closed systems. However, the main constraints in natural open ponds are evaporation losses, requiring large surface of land, pollution from predators and other competitors in the pond, and the inefficiency of the agitation mechanisms resulting in low biomass productivity.
To this end, “raceway ponds” were created, which are operated continuously. In these ponds, the algae, water and nutrients are circulated in a type of racetrack, and are mixed with the aid of paddle wheels, to re-suspend the algae in the water, so that they are in constant movement and always receive sunlight. The ponds are shallow due to the need of algae for light, and that the penetration of sunlight reaches a limited depth.
Photo bioreactors allow the cultivation of a single species of microalgae for a long time and are ideal for producing a large biomass of algae. Photo bioreactors generally have a diameter less than or equal to 0.1 m, because a greater range would prevent light from entering the deeper zones, as the crop density is very high, in order to achieve a high yield. The photo bioreactors require cooling during daylight hours, and also need temperature control at night. For example, the loss of biomass produced at night can be reduced by lowering the temperature during these hours.
The biodiesel production process depends on the type of algae grown, which are selected based on performance and adaptation characteristics to environmental conditions. Microalgae biomass production is started in photo bioreactors, where CO2 that generally comes from power plants is fed. Later, before entering the stationary growth phase, the microalgae are transported from photo bioreactors to tanks of greater volume, where they continue to develop and multiply, until the maximum biomass density is reached. The algae are then harvested by different separation processes, to obtain algal biomass, which is ultimately processed to extract biofuel products.
For the cultivation of microalgae, virtually sterile purified water is required, as productivity is affected by the contamination of other unwanted species of algae or microorganisms. The water is conditioned according to specific culture medium, also depending on the needs of the system.
The key factors to control the rate of algal growth are:                Light: Needed for the photosynthesis process        Temperature: ideal range of temperature for each type of algae        Medium: water composition is an important consideration, for example, salinity        pH: usually algae require a pH between 7 and 9 to obtain an optimal growth rate        Strain: each algae has a different growth rate        Gases: Algae require CO2 to perform photosynthesis        Mixing: to avoid algae settling and warranty homogeneous exposition to light        Photoperiod: cycles of light and darkness        
Algae are very tolerant to salinity, most of the species grow better with a salinity that is slightly inferior to the salinity found in the algae's natural environment, which is obtained by dilution of seawater with fresh water.
Drinking Water Industry
The water industry provides drinking water to residential, commercial, and industrial sectors of the economy. In order to provide potable water, the industry generally begins its operations with the collection of water from high microbiological quality and clarity natural sources, which is then stored in reservoirs for future use. The water can be stored for long periods of time in the reservoir without being used. The quality of water stored for long period of time begins to deteriorate as microorganisms and algae proliferate in the water, making the water unsuitable for human consumption.
Since the water is no longer suitable for consumption, it must be processed in a potable water treatment plant, where it passes through various stages of purification. In the purification plants, chlorine and other chemicals are added in order to produce high quality water. Reaction of chlorine with the organic compounds present in the water can produce several toxic by-products or disinfection by-products (DBP). For example, in the reaction of chlorine with ammonia, chloramines are undesired by-products. Further reaction of chlorine or chloramines with organic matter will produce trihalomethanes, which have been indicated as carcinogenic compounds. Also, depending on the disinfection method, new DBPs have been identified, such as iodinated trihalomethanes, haloacetonitriles, halonitromethanes, haloacetaldehydes, and nitrosamines. Furthermore, exposure of bathers to chlorine and organic matter has been mentioned as a factor contributing to potential respiratory problems, including asthma.
Wastewater Industries
Wastewater is treated every day to produce clean water used for different purposes. There is a need to treat wastewater producing small amounts of sludge and waste, and also using less chemicals and energy.
Mining Industry
Mining is a very important industry throughout the world, and highly collaborates to each nation's economy. Mining industries require water for many of their processes, a resource that is limited and that everyday becomes scarcer. Some mining industries have developed technologies for utilizing seawater in the majority of their processes, being able to operate only with this resource.
The mines themselves are generally located at great distances and heights from the coastal line, therefore the water has to travel many kilometers to reach the mines. To transport the large quantities of water, pumping stations have been constructed, along with very long pipes, in order to pump the water from the sea to the mines.
The pumping stations consist on structures that comprise high power pumps, which send the collected seawater to the next pumping station, and so on. The pumping stations also comprise a containing structure to maintain seawater in case of any problems that could occur in the previous pumping stations. These containing structures eventually can develop diverse problems that affect the pumping process, like the biofouling of the walls and the inner surfaces of the pipes. Biofouling causes the deterioration of the materials as well as a reduction of the transversal area of the pipes, imposing higher operational and maintenance costs. Also, the water inside of the containing structures begins to deteriorate because of the microalgae growth, which negatively interferes with the station processes, and leads to diverse and important problems such as biofouling.
Industrial Liquid Residuals Treatment
Some industries have liquid residuals that may not comply with irrigation, infiltration, or discharging requirements imposed by local government. Also, some industries have settling tanks or other containment means to allow natural processes in the water to occur, such as the emission of gases or other substances that cause bad odor or color properties.
As discussed above, current methods and systems for treating water for industrial uses have high operating costs, require the use of large amounts of chemicals, are prone to fouling, produce undesirable by-products such as gases and other substances that cause bad odor or color properties, and require filtration of the entire volume of water. Improved methods and systems of treating water for industrial use that are low cost and more efficient than conventional water treatment filtration systems are desirable.
Previous Art
Patent JP2011005463A presents a control system for the injection of coagulants and flocculants in water purification plants. Said system is based in the use of a turbidity sensor that measures the quantity and quality of water before adding the coagulants and flocculants. The system uses a classifier that measures flocculant size after settling and classifies the treated water according to these measurements. According to the turbidity measurements, the control system calculates the coagulant and flocculants injection rate, which are applied by installations destined for this means. The calculations of the dosed compounds are corrected according to a function that determines a correction factor in accordance to the turbidity measured before and after the treatment. After the settling of the particles, there is a filtration stage that filters the whole treated water volume.
The disadvantages of patent JP2011005463A are that it does not control the organic content or the microorganisms present in the water, as the system does not comprise the use of disinfectant or oxidizing agents. Also, the system in JP2011005463A does not reduce the metal content in the water and relies on the constant measure of the parameters, therefore having high demands in terms of sensors and other measuring devices. Furthermore, patent JP2011005463A requires filtering the totality of the water volume that is treated, which imposes high energy demands and high installation and maintenance costs regarding the system required for such filtration.